<!DOCTYPE html>
<html>
<head>
<script>

function boom()
{
  var r = document.createRange();
  r.setEnd(document.createTextNode("x"), 0);
  window.getSelection().addRange(r);
  document.execCommand("inserthtml", false, "y");
}

</script>
</head>

<body contenteditable="true" onload="boom();"></body>
</html>
